DIMORPHISM OF FERiXS. 



277 



sterile leaves from quite a large patch of the sensitive fern, once 

 in May, and again in June. In July, when the fertile leaves 

 were appearing above the ground, many of them were changed 

 partly or completely into sterile leaves. In all some thirty plants 



Fig. 310. 

 Normal and transformed sporophyll of sensitive fern. 



showed these transformations, so that every concei\able gradation 

 was obtained between the two kinds of leaves. 



567. It is (juite interesting to note the form of these changed 

 leaves carefully, to see how this change has affected the pinnaj 

 and the sporangia. We note that the tip of the leaf as well as 

 the tips of all the pinnae are more expanded than the basal por- 



